Chemistry picture of the week: Dishes

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As chemists, we need to be aware of what sorts of chemicals we are dealing with and how we can dispose of them — and clean up after them — appropriately and safely. We also need to be sure that our glassware is as clean and free of residues and chemicals we did not specifically add so that each reaction or measurement we conduct is as reproducible as possible. After all, one would not bake an apple pie in a dish that was previously used to cook chicken wings without cleaning it. A surprisingly large amount of time doing chemistry is spent doing dishes.

Pictured above is the receptacle I use to store dirty chemistry dishes in. My system is to build up a metal bowl full of dishes before I pause to do them. I find this allows me to accomplish a fair amount before I need to stop, while also not hoarding too much glassware at once. I do have lab mates who will build up entire 20 L buckets (yes, several) full of dishes before they do theirs. For those guilty of doing this, I will only say the following: hoarding glassware is a good way to make your chemistry friends disappear.

The way everybody does their dishes varies from group to group, too. In my old research group, with which I did my Honours, we would first wash most visible residue off with appropriate solvents: often one of the fantastic foursome of water, ethanol, acetone or methanol. For some glassware, this would be good enough, and after drying, the glassware would be ready to go. For glassware full of stubborn precipitates, we would dunk them in the base bath (made from mixing potassium hydroxide and isopropanol; the “recipe” for base baths also varies from group to group) overnight. Rinsing with copious amounts of water and drying would then leave the glassware good as new — except for the fact that base baths work by dissolving a layer of glass. Any glassware should not be left in the base bath for extended periods of time. Additionally, glassware susceptible to fracturing or implosion should be dealt carefully when washed in the base bath repeatedly.

The group I did undergraduate work with dealt with sensitive rare earth chemistry as opposed to the largely aqueous metallosupramolecular chemistry I did in my Honours and do now. As such, our wash-up regimen was a bit more rigorous, too. Before glassware was left in the base bath, it would be dunked in an acid bath overnight. I would tell you what it was composed of, but I realise now I never bothered to find out. I suspect it was a solution of hydrochloric acid of some concentration. The rationale was, I believe, that the acid bath would dissolve any metal residues left on the glassware, while the base bath would resolve any organic residues. The base bath was followed by a rinse with first water and then acetone, followed by drying in an oven for at least 24 h, due to the water-sensitive nature of our chemistry.

My current group has deemed the corrosive, flammable base baths an unnecessary hazard for the work we do. For thorough cleaning, we use a detergent and hot water, followed by ethanol if some residue happens not to be entirely water-soluble. To someone used to using base baths to clean stubborn glassware, I have found this method surprisingly effective and safe, comparatively. We let our glassware drip-dry overnight, and then it will be good to go again. Very occasionally, some glassware will require more rigorous cleaning — such as glass frits used for compounds insoluble in common solvents. But I would not say this is often the case.

The way we clean our dishes definitely depends on the kind of chemistry that we do. For sensitive chemistry, more rigorous regimens are required. For less sensitive chemistry, the risks and hazards of those rigorous regimens may outweigh any gain. All groups have their own tips and tricks — we could certainly learn from each other here. If you are a chemist, weigh in: how do your dishwashing procedures vary from the ones I’ve learnt?

You can reach me in the comments, by my Twitter account @Lady_Beaker or by e-mail, at chemistryintersection@gmail.com.

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